Poster Presentation 8th Modern Solid Phase Peptide Synthesis & Its Applications Symposium 2022

Investigating the Biosynthesis of Dha/Dhb in Lexapeptide. (#149)

Emily S. Grant-Mackie 1 , Margaret A. Brimble 1 , Paul W.R. Harris 1 , Ghader Bashiri 1
  1. University of Auckland, Auckland, AUCKLAND, New Zealand

Antimicrobial resistance is now one of the leading health concerns of the modern era, with many of our clinical antibiotics struggling to combat this global issue.1 This has led scientists to look towards nature for other possible defences against the present growing crisis. One such promising source is that of the antimicrobial peptide family, the ribosomally synthesised and post-translationally modified peptides (RiPPs).2 Lanthipeptides, exemplified by the food preservative nisin, are an important sub-class of RiPPs and contain lanthionine (thioether) bridged polycyclic structures as well as α,β-unsaturated amino acids, usually 2,3-dehydroalanine (Dha) and (Z)-2,3-dehydrobutyrine (Dhb).3 This family of peptides has a wide range of activities from antibacterial to anticancer.3 Lexapeptide is a novel lanthipeptide discovered in 2016 containing many of the same structures found in other lanthipeptides including a (2S,6R)-lanthionine (Lan) ring, two Dha and two Dhb residues.4 Lexapeptide also contains some rarer structural moieties: an N-terminal (N,N)-dimethyl phenylalanine, a C-terminal (2-aminovinyl)-3-methyl-cysteine (AviMeCys) and a D-alanine, Lexapeptide also has potent antibacterial properties against Gram-positive bacteria.4 It is known that the Dha/Dhb residues are added using the enzymes LxmK/LxmY however the biosynthetic pathway for installing these residues are poorly understood, therefore we have attempted to elucidate the specific precursor substrates and the order-of-events during which the residues are formed. Enzyme assays were carried out using various precursor lexapeptide analogues and either of LxmK or LxmY in different combinations, with the reaction products monitored with HPLC and identified using mass spectrometry. Although no enzyme reaction products were detected within the assays other than the starting materials, valuable insights into the acid/base stability of the enzymes as well as the stability of synthetic lexapeptide analogues has spurred further investigation and given us a better understanding of how these enzymes play their part in the biosynthesis of lexapeptide.

  1. (1) Nolte, O. Antimicrobial Resistance in the 21st Century: A Multifaceted Challenge. Protein Pept. Lett. 2014, 21 (4), 330–335.
  2. (2) Mahlapuu, M.; Håkansson, J.; Ringstad, L.; Björn, C. Antimicrobial Peptides: An Emerging Category of Therapeutic Agents. Front. Cell. Infect. Microbiol. 2016, 6.
  3. (3) Ongey, E. L.; Neubauer, P. Lanthipeptides: Chemical Synthesis versus in Vivo Biosynthesis as Tools for Pharmaceutical Production. Microb. Cell Factories 2016, 15 (1), 97.
  4. (4) Xu, M.; Zhang, F.; Cheng, Z.; Bashiri, G.; Wang, J.; Hong, J.; Wang, Y.; Xu, L.; Chen, X.; Huang, S.-X.; Lin, S.; Deng, Z.; Tao, M. Functional Genome Mining Reveals a Class V Lanthipeptide Containing a D-Amino Acid Introduced by an F420 H2 -Dependent Reductase. Angew. Chem. Int. Ed Engl. 2020, 59 (41), 18029–18035.